Sleep apnea (SA) is the most common disorder observed in the practice of sleep medicine and is responsible for more mortality and morbidity than any other sleep disorder. SA is characterized by recurrent failures to breathe adequately during sleep (termed apneas or hypopneas) as a result of obstructions in the upper airway.
Nocturnal polysomnography (PSG) is often used for sleep apnea diagnosis. PSG studies are performed in special sleep units and generally involve monitoring several physiological recordings such as electrocardiograms (ECG or EKG), electroencephalograms (EEG), electromyograms (EMG), electrooculograms (EOG), airflow signals, respiratory effort, and oxygen saturation (SaO2) or oximetry. These signals are typically manually analyzed by a sleep specialist to identify every episode of apnea/hypopnea. The number of detected events is divided by the hours of sleep to compute the apnea-hypopnea index (AHI), which is used to assess a subject's sleep apnea severity. PSG studies, however, have drawbacks since they are costly, time-consuming, and require subjects to remain overnight in a medical facility, or other room (e.g., office, hotel room), connected to monitoring equipment by a multitude of wires. Current PSG sleep studies monitor motion/movement by using video cameras and sleep technicians manually observing movements after the sleep study. Some sleep studies use actigraphy watches that cost $1,000, with $400 software licenses.
The last few years have seen increased demand for better breathing/sleep diagnostics. There has been more focus on home breathing/sleep monitoring techniques. These techniques monitor the subject's air flow, EKG and pulse oximetry. As such, these techniques require relatively expensive equipment (e.g., $400 to $1,000) that is very bulky and requires many wires to be connected between the equipment worn by the test subject (e.g., headgear, Holter monitor) and the diagnostic equipment. As can be appreciated, the bulkiness of the equipment worn by the subject and the need to maintain the multitude of wired connections throughout the study makes the study very uncomfortable for the test subject. Should the subject desire to get out of bed during the study (e.g., a trip to the bathroom, a desire to walk around, etc.), all of the wires would need to disconnected and then reconnected to continue the study. Moreover, the study is prone to errors or may even need to be re-done should one or more wires become disconnected during the study. All of these scenarios are undesirable for both the subject and the medical facility.
Patient surveillance and telemedicine have an increasing importance in providing appropriate and timely healthcare services. Current patient reporting outcomes require a patient to complete surveys/questionnaires using paper-based methods inside a clinic even though remote mobile technologies allow for simpler data collection using digital tools and mobile devices. As patients are discharged from a medical facility to their home, important patient outcomes may be missed due to lack of reporting modalities and surveillance and result in costly hospitalizations. In addition, the last few years have seen the introduction of stylish wrist-worn monitors that count the number of steps even though cheap consumer pocket pedometers have been around for years. These stylish wrist-based pedometers are mere novelties that do not offer real utility in monitoring either health or wellness measures. The potential utility of such devices is also not maximized since on-board, embedded algorithms can be costly and require significant battery and memory, which are limited given the stylish form factor of these devices.
Accordingly, there is a need and desire for a better monitoring technique that overcomes the above-noted limitations associated with PSG, Holter monitors and home monitoring techniques.